curvature versus slope
  n = 205947 
  X=0, Y = 22.01 +/- 16.46 
  Weighted least-squares fit:  Y = 45.5 + 2.458 X  + -0.02651 X**2 

slope versus dZ, curvature < 5
  n = 31203 

  Weighted least-squares fit:  Y = 4.4 + 0.651 X  + 0.00063 X**2 
     at X = 100, Y = 75.8 
     effective RMSE xy = 118.9 

slope versus dZ, curvature < 15
  n = 61106 

  Weighted least-squares fit:  Y = 5.4 + 0.713 X  + -0.00045 X**2 

curvature versus dZ, slope < 10
  n = 14204 
  X=0, Y = 8.69 +/- 6.83 
  Weighted least-squares fit:  Y = 8.6 + 2.549 X  + 0.04475 X**2 


Number of samples 210484
Max dz = 900
Mean dz = 51
RMS dz = 90.9175450614
100cm = 85.9851580168 percentile value of dz